Field of the Invention
The present invention relates generally to electrically operable security systems in which a door is unlocked by accessing an electronic control system, and more particularly to an improved electrically operable door lock which may be installed on a door through which access is to be controlled by an electrically operable security system, whereby the door opening mechanism is selectively locked and unlocked by controlling the supply of electricity to the door locking mechanism to thereby control access or egress through the door.
Security doors to prevent theft or vandalism have evolved over the years from simple doors with heavy duty locks to more sophisticated egress and access control devices. Hardware and systems for limiting and controlling egress and access through doors are generally utilized for theft-prevention or to establish a secured area into which (or from which) entry is limited. For example, stores use such secured doors in certain departments (such as, for example, the automotive department) which may not always be manned to prevent thieves from escaping through the door with valuable merchandise. In addition, industrial companies also use such secured exit doors to prevent pilferage of valuable equipment and merchandise.
One type of door lock which has been used in the past to control egress and access through a door is an electromagnetic system which utilizes an electromagnet mounted on a door jamb, with an armature mounted on the door held by the electromagnet to retain the door in the closed position when the electromagnet is actuated. Such locking mechanisms are illustrated in U.S. Pat. No. 4,439,808, to Gillham, U.S. Pat. No. 4,609,910, to Geringer et al., U.S. Pat. No. 4,652,028, to Logan et al., U.S. Pat. No. 4,720,128 to Logan, Jr., et al., and U.S. Pat. No. 5,000,497, to Geringer et al. All of these references utilize an electromagnet mounted in or on a door jamb and an armature on the door held by the electromagnet to retain the door in the closed position. Such electromagnetic locking systems are quite effective at controlling egress and access through the door they are installed on. Unfortunately, however, such systems are quite expensive, and require a fairly complex installation, often with the electromagnet being mounted in the door jamb.
Another type of system which is known in the art is the electric door strike release mechanism, in which a latch bolt located in and extending from a locking mechanism located in a door is receivable in an electrically operable door strike mounted in the frame of the door. The door may be opened either by retracting the latch bolt into the locking mechanism to thereby disengage it from the door strike, or by electrically actuating the door strike mechanism to cause it to open and to thereby release the extended latch bolt from the door strike mechanism. Typically, such electrically operable door strikes pivot to allow the door to close without the door strike mechanism being electrically actuated. Such door strike mechanisms are illustrated in U.S. Pat. No. 4,017,107, to Hanchett, U.S. Pat. No. 4,626,010, to Hanchett et al., and in U.S. Pat. No. 5,484,180, to Helmar. Like the electromagnet/armature systems discussed above, electrically operated door strike systems are also expensive, and require a significant installation into the door jamb, which must usually be reinforced.
It is accordingly the primary objective of the present invention that it provide an electrically operable door lock apparatus, and a method for the operation thereof, which may be installed into a standard door in place of a regular lockset. It is a related objective of the electrically operable door lock apparatus of the present invention that it comprise a single module which may be easily installed in the conventional manner into a door (save for the installation of a pair of wires), with a standard strike plate (and no other apparatus) being mounted in the door frame. It is an additional objective of the present invention that the electrically operable door lock apparatus may be operated by turning a knob or handle in a manner like that of a conventional lockset, except that the use of the knob or handle to open the door may be selectively enabled or disabled through the use of the electrical locking mechanism.
It is a further principal objective of the electrically operable door lock apparatus of the present invention that it be selectively adaptable to operate in either a fail safe mode of operation in which the door will be locked when electrical power is supplied to the door lock apparatus and unlocked when electrical power is not supplied, or a fail secure mode of operation in which the door will be unlocked when electrical power is supplied to the door lock apparatus and locked when electrical power is not supplied. It is a related objective of the present invention that these two alternate modes of operation be user selectable prior to installation of the electrically operable door lock apparatus into the door without requiring the use of additional or alternate components. It is yet another related objective of the electrically operable door lock apparatus of the present invention that the selection of the operating mode be relatively easy to accomplish using only simple hand tools.
The electrically operable door lock apparatus of the present invention must be of a construction which is both durable and long lasting, and it should also require little or no maintenance throughout its operating lifetime. In order to enhance the market appeal of the electrically operable door lock apparatus of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the electrically operable door lock apparatus of the present invention be achieved without incurring any substantial relative disadvantage.